Breath analysis for medical diagnosis

Breath analysis for medical diagnosis using a versatile infrared spectrometer
More than 2000 years ago, Greek physicians already knew that the aroma of human breath could be used for medical diagnosis. A well-known example is the sweet odor caused by acetone in the breath of people with uncontrolled diabetes. The modern era of breath analysis started in 1971 with the work of two-time Noble Prize winner Linus Pauling. He accumulated the gas of 10 to 15 exhalations in a cold tube. Upon heating the tube the released gas was analyzed using gas chromatography revealing the presence of 250 substances. Accumulation was required as most molecules are only present at the parts per billion level or even below. However, there are several problems associated with the accumulation process, in particular the low reproducibility and the low time-resolution.
The accumulation step has become superfluous with the versatile and sensitive spectrometer which VSL developed within the framework of a EURAMET joint research project `Breath analysis as a diagnostic tool for early disease detection’. The spectrometer is based on a special mid-infrared light source in combination with the detection method cavity ring-down spectroscopy (CRDS). Basically in CRDS a light pulse is trapped in a cell consisting of a pair of highly reflecting mirrors. A small amount of this trapped pulse will leak out the cell during each round trip resulting in an exponential decaying light intensity inside the cell. With a breath sample present inside the cell, the light intensity decreases faster at the wavelengths where the gas absorbs the infrared light. The high sensitivity results from the long effective absorption path length which exceeds 3 kilometers in our spectrometer. The versatility of the spectrometer stems from the widely tunable infrared light source (2700 till 3500 nanometer) enabling detection of more than one hundred different compounds.
The project addresses the lack of accuracy and reliability in current breath measurement results. For a selected set of biomarkers we are on the way to reduce the uncertainty of measurement from the current typical 10% down to at most 1-2%, taking into consideration the presence of interfering components in breath. In the spring of 2011 a symposium will be organized bringing together research groups in the medical and clinical field, equipment manufacturers, and experts in the field of laser spectroscopy to discuss the outcome of the project.

For more information about the VSL spectrometer or on the upcoming symposium, contact Dr. Stefan Persijn (spersijn@vsl.nl)



The widely tunable mid-infrared source (2700-3500 nm) used in the spectrometer developed by VSL.